In general, this invention relates to video signal apparatus. More particularly, this invention relates to apparatus for processing time-divisionmultiplex video signals which have a buffer segment between video component segments.
Consumer video cassette recorders (VCR) typically use a "color-under" format to minimize color image problems which may result from the direct recording of a composite color video signal on magnetic tape. In the "color-under" format, the luminance component of the video signal is converted to an FM signal and the chrominance component is converted to a lower frequency signal outside of the frequency band of the FM luminance signal. The "color-under" format has several disadvantages. Thus, the resolution of the image is reduced due to reduction of the luminance bandwidth. In addition, color inaccuracies may result from the poor chrominance signal to noise ratio and from errors in the generation and regeneration of the standard composite color subcarrier signal.
In order to minimize these disadvantages of the "color-under" format, it has been proposed in U.S. Pat. No. 4,335,393, issued June 15, 1982, for "METHOD AND SYSTEM USING SEQUENTIALLY ENCODED COLOR AND LUMINANCE PROCESSING OF VIDEO TYPE SIGNALS TO IMPROVE PICTURE QUALITY", patentee G. J. Pearson, to reformat the concurrent luminance and chrominance components of a composite color video signal into a signal having compressed luminance and chrominance signals which are sequential in time to one another. The time sequential signal is then recorded on magnetic tape. This patent also discloses insertion of a mezzanine signal of fixed voltage level between the sequential chrominance and luminance components to serve as a dynamic reference for subsequent processing of the chrominance component. A somewhat similar technique is disclosed in U.S. Pat. No. 4,084,181, issued Apr. 11, 1978, for "APPARATUS FOR TRANSMISSION OF CHROMINANCE SIGNALS DURING BLANKING PERIOD", in which only the chrominance component signal is compressed in time and inserted during the horizontal blanking period. This patent also discloses insertion of fixed level buffers between the chrominance and luminance signals and between the chrominance and synchronizing signals to reduce crosstalk. In "NTT and NHK Home Systems for Sharp TV", ELECTRONICS, July 14, 1983, pages 82-3, there is disclosed a high definition color video signal in which the chrominance signal is compressed and transmitted sequentially in time relative to the luminance signal. A fixed level guard signal is inserted between the two signals.
In the transmission of a time-division-multiplex video signal over an analog transmission path, the limited response time of the analog path to large changes in signal value, may cause distortion of a sequentially transmitted component signal resulting in degradation and color changes in a reproduced image. Although, in each of the above systems a fixed level buffer is used to isolate components of the video signal processed by the system, the fixed level of the signal during the buffer does not always insure that the signal reaches an appropriate value before transmission or production of the next signal component.